Actualistic approach to the chemical preservation potential and its influence on the Caenogastropoda biodiversity

Abstract

The Cretaceous Period is characterised by a peak in ocean surface acidity, which may have altered the fossil representation of its marine biota. Thus, we propose to study the dissolution of Caenogastropoda shells and to verify the number of fossil occurrences of the respective families during the Cretaceous, aiming to produce insights on which groups present a higher chemical preservation potential in low pH environments. An experimental taphonomy approach was used to obtain the mass loss rate of 12 shells without taphonomic damage. Morphometric measurements were conducted, and each shell was subjected to a solution of acetic acid diluted in distilled water, remaining for 24 h. At each interval of four and eight hours, the samples were dried, weighed, and pH of each container was checked. As result, it was recognised that the samples with lower dissolution rates, in other words more resistant to the chemical conditions of the simulated benthic taphonomically active zone, are those that distribute the shell mass over a smaller surface area. This corroborates with the high occurrence of their respective families during the Cretaceous. The Caenogastropoda shells that show the highest chemical preservation potential, therefore, are those with the lowest surface area to mass ratio.